<script src="vue.js"></script>

<div id="app">
    <div v-bind:class="{box}">我是box
        <div v-bind:class="{inner}">我是inner1</div>
        <div v-bind:class="{inner}">我是inner2</div>
    </div>
</div>

<script>
    var vue=new Vue({
        el:'#app',
        data:{
            box:'box',
            inner:'inner'
        }
    });
</script>

<style>
    .box{
        background-color: pink;
        width: 100%;
        height: 100%;
    }
    .inner{
        background-color: red;
        width: 80px;
        height: 100px;

    }
</style>